The present invention relates to a novel apparatus for causing pressure equalization between flow masses in two regions, and a method for achieving said equalization. The apparatus utilizes a wall or surface between the flow masses, said surface containing a plurality of perforations, and achieves equalization by the exchange of flows through the perforations.
The need to equalize fluid flow in a given region is well known. The term xe2x80x9cfluidxe2x80x9d in this instance may refer to air, gas, or liquid. One of the most important applications of equalizing flow is in the area of turbine engines to diminish flow distortions or the occurrence of compressor surge and rotating stall.
Gas turbine engines require high performance and high reliability in order to assure that flights can be completed effectively, efficiently and safely. This is especially true in military applications. Air is forced through the inlet or mouth of a turbine engine and from there directed into a compressor. As the flow in the compressor is reduced or made non-uniform while the compressor or rotational speed is held constant, a point will be reached at which some or all of the engine blades begin to stall and engine instabilities occur. The most violent of these is xe2x80x9csurgexe2x80x9d, which for high speed compressors (as in a turbine engine) can result in periodically reversed flow and mechanical damage. The other result of air being reduced or made non-uniform is rotating stall. xe2x80x9cStallxe2x80x9d can result in a region of blocked flow covering half of the circumference of the engine inlet and rotating at half the rotor speed, and may lock the engine.
When a gas turbine engine experiences a compressor xe2x80x9cstallxe2x80x9d or xe2x80x9csurgexe2x80x9d, the given flight will be effected. In cases of severe surge, the engine or drive train components can fail, causing loss of engine operation. When this happens in flight, the results can be catastrophic. Similarly, a rotating xe2x80x9cstallxe2x80x9d can lock or freeze an engine resulting in loss of operation. For an in depth discussion of how a turbine engine works, and turbine engine surge and stall, see Emmons, H. W., Pearson, C. E., and Grant, H. P.; xe2x80x9cCompressor Surge and Stall Propagation,xe2x80x9d Transactions of the ASME, May, 1955, p. 455-469; and Greitzer, E. M., xe2x80x9cThe Stability of Pumping Systemsxe2x80x94the 1980 Freeman Scholar Lecture,xe2x80x9d ASME J. of Fluids Engineering, June., 1981, vol. 103, p. 193-242.
Surge and stall are commonly caused by: (1) engine deterioration; (2) aerodynamic distortions (especially at the air inlet); and (3) hot gas injection (from weapon firing). Despite the knowledge of these causes, there has been little success in providing turbine engines with any reliable way of preventing engine surge or stall.
The present invention addresses cause number (2), and teaches a way to create a flow of air into a turbine engine which is uniform in pressure around the circumference of the engine inlet. As air enters an engine inlet, any variations in pressure at different points around the circumference of the inlet create aerodynamic disturbances and mechanical stress, hence inefficiencies in the engine. If the introduced air is non-uniform in pressure, the stress on the blades of the engine will also be non-uniform, because the blades of a turbine engine are rotating and acting on the introduced air. This stress on the engine causes blade shape deformation, which may further deteriorate the engine and cause the engine to run inefficiently. Uniform pressure around a turbine engine inlet will assure that the flow of air into the engine is constant and uniform, and will reduce engine stress while increasing engine efficiency.
Accordingly, an object of the present invention is to provide an apparatus that may cause fluid pressure in one region to equalize with the pressure in another region.
It is a further object of the present invention to provide an apparatus for equalizing the pressure of air around the inlet duct of a turbine engine.
Still another object of the present invention is to provide a method for equalizing the pressure of air around the inlet duct of a turbine engine.
All publications and references cited herein are hereby incorporated into this specification by reference thereto.
In accordance with these and other objects of the present invention, an apparatus is provided comprised of a means for detecting and regulating the pressure in a first flow area, said first flow area separated from an adjacent second flow area by a surface or wall containing a plurality of perforations. A method for regulating the fluid pressure in said second flow area is also provided, said method comprised of controllably regulating the fluid pressure in said first flow area and permitting fluid to freely flow between said flow areas through said perforations in said surface or wall.
This apparatus and method provides a simple and efficient means to assure pressure equalization in the air around the circumference of the inlet duct of a turbine engine, and thereby reduce or eliminate aerodynamic distortions at said inlet duct.
The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its structure and its operation together with the additional object and advantages thereof will best be understood from the following description of the preferred embodiment of the present invention when read in conjunction with the accompanying drawings. Unless specifically noted, it is intended that the words and phrases in the specification and claims be given the ordinary and accustomed meaning to those of ordinary skill in the applicable art or arts. If any other meaning is intended, the specification will specifically state that a special meaning is being applied to a word or phrase. Likewise, the use of the words xe2x80x9cfunctionxe2x80x9d or xe2x80x9cmeansxe2x80x9d in the Description of Preferred Embodiments is not intended to indicate a desire to invoke the special provision of 35 U.S.C. xc2xa7112, paragraph 6 to define the invention. To the contrary, if the provisions of 35 U.S.C. xc2xa7112, paragraph 6, are sought to be invoked to define the invention(s), the claims will specifically state the phrases xe2x80x9cmeans forxe2x80x9d or xe2x80x9cstep forxe2x80x9d and a function, without also reciting in such phrases any structure, material, or act in support of the function. Even when the claims recite a xe2x80x9cmeans forxe2x80x9d or xe2x80x9cstep forxe2x80x9d performing a function, if they also recite any structure, material or acts in support of that means of step, then the intention is not to invoke the provisions of 35 U.S.C. xc2xa7112, paragraph 6. Moreover, even if the provisions of 35 U.S.C. xc2xa7112, paragraph 6, are invoked to define the inventions, it is intended that the inventions not be limited only to the specific structure, material or acts that are described in the preferred embodiments, but in addition, include any and all structures, materials or acts that perform the claimed function, along with any and all known or later-developed equivalent structures, materials or acts for performing the claimed function.